just put a auxilari winding on the rotor (in the salient pole)..
Yes, that is one of the major advantages of a three-phase induction motor.
Split Phase Induction Motor.
A three-phase motor has a steady rotating magnetic field generated by the stator coil, and the rotor just follows the field.
Three Phase Induction Motor is self starting motor so you can start it by conneting to power lines directly if the power line capacity is sufficient.
The single phase induction motors are made self starting by providing an additional flux by some additional means. Now depending upon these additional means the single phase induction motors are classified as: 1.Split phase induction motor. 2.Capacitor start inductor motor. 3.Capacitor start capacitor run induction motor. 4. Shaded pole induction motor.
Single phase induction motor is not self starting because, when the main winding is excited from a single phase supply, it produces an alternating magnetic field instead of rotating magnetic field in two phase and 3 phase induction motor. According to double field revolving theory any alternating vector can be resolved into two vectors rotating in opposite directions, each having magnitude equal to one half the magnitude of the actual vector. The vectors will be rotating in such a way that their resultant will be zero at every instant. Thus a single phase induction motor fails to produce a net starting torque, and is not self starting.It can be made self starting by any of the methods below1) By using an aux winding in series with a very high resistance2) using two capacitors,in series with the aux wdg,one with intermittent duty and the other one with continuous duty3) Using shaded poles
Three Phase Induction Motor is self starting motor so you can start it by conneting to power lines directly if the power line capacity is sufficient.
A single phase induction motor is not self starting; thus, it is necessary to provide a starting circuit and associated start windings to give the initial rotation in a single phase induction motor. The normal running windings within such a motor can cause the rotor to turn in either direction, so the starting circuit determines the operating direction.
There are 5 types of starting in induction motors: 1) resistance variable method 2) auto transformer method 3) slip ring induction motor method Squirrel cage induction motor using two types of starting methods 1.Direct on line starter 2.Star delta starter
A single phase induction motor is not self starting; thus, it is necessary to provide a starting circuit and associated start windings to give the initial rotation in a single phase induction motor. The normal running windings within such a motor motor can cause the rotor to turn in either direction, so the starting circuit determines the operating direction.
Mostly capacitor is used in the induction motors to improve the power factor , and make them to work as a self starting machine. In the small size , capacity dc motor has capacitor across it to smooth running without spark
A brushless DC motor is self-starting using only one magneto-sensitive element because the motor is of a two-phase type and is provided with a detection device which detects towards which of the two phases the rotor is mainly directed. A presetting circuit compares the detected rotor position with the state of an energizing circuit in order to set this circuit so that the energizing circuit energizes the stator phases for said specific rotor position in such a way that starting of the motor is guaranteed, although initially with an undefined direction of rotation. By presetting the commutating direction of the energizing circuit the rotor subsequently locks onto the field and rotates in the correct direction if it has started in the incorrect direction